1. Field of the Invention
The present invention generally relates to high speed document handling systems and, more specifically, to a method and a set of gauges for aligning and focusing the imaging devices used in a high speed document handling system.
2. Description of the Prior Art
High speed document handling systems are used to quickly capture and store information present on the surfaces of a document. After the information has been captured, the information can be processed at remote stations without physically transferring the document. High speed document handling systems have been in use in the banking industry to process checks, in the credit industry to process credit card receipts, and in wholesale and retail operations to process remittance documents.
Early automated document handling systems required the documents to contain coded data which could be read by a bar code reader or similar device. Because many documents are handwritten, document handling systems which rely on coded information have limited utility.
Recently, much effort has been made to adapt image capturing and character recognition schemes for use in a high speed document handling system. In operation, a document is imaged using a light source to illuminate the document and a photodetector or camera array to receive light reflected from the document as the document is moved through a track past the imaging station at high speed. After the document has been imaged, the signals from the photodetector or camera array can be analyzed to determine and store the information on the document.
Correct operation of the imaging system is critical to the performance of any high speed document handling system. Improper alignment of the light sources and the photodetector array and/or improper focussing of the light will reduce the intensity of light received by the photodetector array and make the information on the document indistinguishable from background noise. In the past, it has been the practice to merely drop a piece of white paper within the track of the document handling system and to adjust the optics to maximize the peak signal output from the photodetector array. This method of alignment and focussing leads to mixed results since there is no control over the precise placement of the white paper within the track. In one calibration run, the white paper may be positioned closer to the front wall of the track while in another calibration run, the white paper may be positioned closer to the rear wall of the track. In addition, the white paper could be positioned at an angle within the track. Without knowing the precise position of the white paper in the track, a technician is liable to set the light output too high such that information received by the photodetector will be lost because of saturation of the analog to digital (A/D) converter.